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All About GT550 Gauges

Contributed by Allan Tucker

For the first two years of the GT550 (1972 and 1973) the instrument cluster consists of a pair of gauges with a speedometer mounted on the left and a tachometer on the right. They are both housed together in a black textured main case with rubber surrounds. In the central portion of the main case between the two gauges is the amber turn signal lamp with the chromed 'S' emblem above it, no doubt the speed warning lamp for the JDM market would be situated in the emblems location as was done on the GT750 model. It's easy to assume a decal is placed under the 'S' emblem when the speed warning lamp is mounted as the finish of the case there is smooth. (Editors note: I am still trying to confirm this as all photos of JDM models seen so far have the 'S' emblem where the light should be. Given the low production numbers it is possible that examples seen to date are foreign models re-imported back into Japan) Centrally mounted below the turn signal lamp is the ignition switch.

The photos show a set of restored gauges and main case for a 72/73 GT550 in mph scale. This case is missing the rubber surrounds.

The textured main case has two removable rubber surrounds on each gauge that look like goggles of sorts, their primary purpose is to help reduce glare during bright sunlight. These rubber surrounds are kept in place by the addition of a thin plastic trim that’s glued to the main cases top edge. These flimsy trim pieces often get broken, which means the rubber surrounds can no longer be attached to the gauge case. On the lower facing side of the gauge housing are two stainless steel cups that conceal the lower portions of the gauges and other items such as wires used for the illumination bulbs etc.

The gauges are screwed into the main case by four screws, held on by brass inserts moulded into the main case. They are rubber mounted onto the main metal bracket, which in turn is kept in place by sandwiching the gauges to the main bracket by the stainless cups below.

The gauges are made by Nippon Seiki Japan, the speedometer has the odometer scale in the upper portion with a trip meter feature and its scale in the lower portion of the face. The complete gauge unit is housed in a white plastic case using an integrated acrylic lens with a convex shape.The gauge's face colour is a type of deep blue with cream/yellow markings for segments and numerals. Speedometers register up to 150 mph or the metric equivalent depending on the market they were destined for, and so far there’s no evidence to suggest a dual scale speedometer unit exists for the first two years.

The trip knob is plastic with a serrated finish for easy gripping, and is attached by a single screw to the shaft's end that then passes through a rubber boot glued into the white case.

The tachometer has the deep blue coloured face with cream/yellow markings for the segments and numerals. The red-line section starts at 8000 rpms but those segments of the scale are coloured in a medium red. In the lower portion of the face there are two warning lamps, the green neutral lamp coded 'N' is on the left while the red high beam coded 'B' is in the lower right section.

As is customary during this time period both gauge faces have the Suzuki 'S' logo on them just below the needle boss area. The needles are made of pressed brass with a brass boss and the top cap in chrome, the brass portions are painted white with a bright red fluorescent tip.

These early internal gauge mechanisms are very similar in appearance to those also used in the 1970 T500 model, These are very durable units, everything is made of metal internally except the reels for the odometer and some parts of the trip mechanism. The odometer reels can be removed by simply taking out a clip, most other types of speedometers have the reel shaft pinned into the mechanisms frame. They carry a single illumination bulb in each unit and the mechanism itself is screwed to the metal base plate by two screws. The metal base plate is then fixed into the white plastic case which is then fused around it.

Age has not been kind to the acrylic lenses, the suns rays and UV factors have wreaked havoc on the material leaving it in very poor condition 40 years on. The only long term remedy is to retrofit glass into the cases, a job requiring some finesse which should only be tackled by someone who is capable of doing such work and restoring all the other related parts while the cases are being repaired.

Below is a photo of a set of gauges installed on a 1974 model - the plastic lenses in this instance have been polished to be usable.

The new for 1974 housing revision was more of a box like shape, finished in a textured matte black with a warning panel mounted in the upper section between the gauges for the turn and high beam lights. Again as was the norm, high beam was a red lens but changed to a blue one in late 1976. Just centrally located below this warning panel was a new gear indicator display of a digital style design, the display illuminates the gear selected in red, mounted behind a smoke coloured rectangular lens.

The round neutral light lens is then mounted below the gear indicator display with the ignition switch just below this as well. The wording for the respective warning lamps is recessed into the case and finished in white.

Japanese domestic market machines included the 80 kph warning lamp in the new warning panel between the high beam and turn signal indicator lights with a decal positioned above the 'Gear Position' indicator lettering as seen in the photo below.

The white plastic housings for the individual gauges from the 72 and 73 models were retained for the 74 and 75 models, screwed into the case in two locations for each mechanism just as was previously done. In 1976 a change was made to the housings and metal cases were designed to house the mechanisms, this time using glass lenses instead of the molded in acrylic lenses in white plastic housings.

Between 1974 and 1975 speedometer units featured a similar dark blue face as was seen on the 72 and 73 models, but the scale of registering was changed as well as the font type. A maximum indicated speed of 150 mph/210 kph was now offered, displayed on a pale blue colour on the dark blue face.

The tachometer also had a revision to is face plate and displayed the redline area on the segments in the respective area of the face. The Suzuki 'S' symbol was retained on the faces, centrally located just below the needle boss area.

The needles on the GT550 initially retained the chrome centre button as was previously used, the GT380 and GT250 models used the same needle design but it's an all white needle.

Of note is the fact there is no provision for the round chrome 'S' button on these later cases used on the GT550.

When the change was made to the metal can type housings between 1976 and 1977, the faces went through some revisions as well, the redline section was updated to a two tone coloured area of red, this redline updated design carried on when the faces went to the brown background for the 77 models.

With the change to brown backgrounds on the faces, the segment and numerals were also changed to a cream/white colour with the interior of the metal cases left unpainted. The photos below show a very late production dual scale brown face set, courtesy of Mike Yeadon in the UK. In earlier versions the face was either in kilometers or in miles.

All the while the changes were being made from 1972 to 1977, the internal gauge mechanisms remained mostly unchanged, some minor little metal parts were changed to plastic, for example the small bushing to hold one side of the odometer shaft, but it's not that significant, but as with unpainted gauge interiors, it's obviously a cost cutting measure.

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